A great debate! I agree with all really - some say when written use 'were' but often, especially with British English and in speech, we use 'if I was'. There is something slightly stunted and archaic about always saying 'if I were'. If I were you, I'd use whichever you have a feeling for, however, if I was you, I would probably not quite know which feeling was correct! :O
On the safe side 'If I were', on the dangerous side, experimenting and ask us for specific examples :)